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Philly BMW Tech
Philly BMW Tech, BMW Master Technician
Category: BMW
Satisfied Customers: 161
Experience:  BMW Master Technician (Level 1) w/ 8 years BMW experience and 15 years experience overall
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2004 745i: with 133,000 miles..fault code..emissions..passenger side

Customer Question

I have a 2004 745i with 133,000 miles. The routing maintenance is up to date. I do have a odb fault code p0491 which I replaced the emissions valve located behind the passenger side head. I was a little clogged so snaked the carbon build up out, but still i have this code. I believe there is an oil leak possible on the valve cover gasket on that head also. My main problem is when the car reaches optimal operating temperature, and I stop at a light from 2 to 3 minuets, i get a puff of blue smoke when i take off. The car runs great, but at times it feels is i there is a vacuum leak. No smoke is present when I start the car, or prior to reaching normal operating temperature. All pcv valves have been replaced. BMW told me compression checks look normal but this has been going on for about 4 months. Please help. Thank You, David
Submitted: 7 years ago.
Category: BMW
Expert:  Philly BMW Tech replied 7 years ago.



I believe that our P0491 code could be caused by a broken secondary air supply tube under the intake manifold. Number 1 in the picture below.

For your smoking issue you might have a vacuum leak sucking oil in, but it is also possible that you have a valve seal issue. Your best bet is to take the car to a shop that can smoke check the intake system and see where the leak is.


Good luck,




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